Method of processing by-product soaps for recovery of their acids free from detrimental alcohols, etc.



l Patented Apr. 30, 1946 METHOD OF PROCESSING BY-PRODUCT soars FOR RECOVERY OF THEIR ACIDS FREE FROM DETRIMENTAL ALCOHOLS,

ETC.

Bonheur M. Weston and Frank F. Beall, Detroit, Mich., assignors to Aristo Corporation, Detroit, Mich., a corporation of Michigan No Drawing. Application April 19, 1943,

Serial N 0. 483,662

6 Claims. (Cl. 260-4975) Our invention comprises a method of recovering in substantially pure state rosin acids and fatty acids from byproduct soaps such as the soap resulting from the manufacture of wood pulp by the caustic soda or sulphate process. a saponified mixture of rosin acids, fatty acids, higher alcohols, and water. Many such crude soaps and crude oils, not necessarily derived from the sulphate process above mentioned, contain free alcohols. These alcohols, commonly sterols,

frequently amount to as much as 10% of the soap stock or crude oil and are detrimental. They are responsible for objectionable odor, have high boiling point, and impede the drying time of oils in which they are contained, and impede production of esters from such oils and drying time thereof. Such alcohols also often completely nullify the efiect of metal driers frequently introduced to expedite drying.

Present methods of recovery of fattyacids from these by-product soap stocks by treatment with sulfuric acid yields unsatisfactory results because the recovered fatty acids are still adulterated with sterols, poor quality pitches, and charred vegetable and animal matter, and, in addition, sulfur 1 compounds are formed which become fixed in'the oil. All these adulterants limit the usefulness of the oil. Furthermore, the elimination of these inert and detrimental materials from the oils -resulting from the sulphuric acid treatment is diff iicult because they become a more fixed combination in the oils than they were in the soap stock, and it is costly because they can then be removed only by expensive treatment.

By the use of our invention, these inert and I detrimental materials may be easily and cheaply This is not alwaysnecessary. A predetermined amount of crude soap stockis charged into the vessel together with suflicient water to form an easy working emulsion. The mixture is heated with steam to boiling temperature 212 F. and agitated. When the emulsion is substantially complete, a

, 26% brine solution is introduced into the vessel.

removed from the soap stocks and the fatty acids and rosin acids recovered economically in relatively pure form.

Our process may be carried out with conventional equipment and we have found to be most practical a non-pressure acid resisting type of reaction vessel set in a water jacket which is heated by any suitable means. Steam generated either in the water jacket or separately is carried into the vessel by suitable means such as a pipe coil having perforations to permit the escape of steam. The coil is placed in the bottom of the vessel so that it not only provides steam for the reactions upon which the process depends, but so that the steam inescaping will aid in agitating the material .being treated. A power-driven agitator is proltion is usually desirable at the beginning although The amount of brine added will be dependent upon the type of soap being processed and the amount of water added. For instance, where color can be disregarded and a high yield of soap is desired, the salt brine solution may be added until the saltconcentration ofthe Wash water or free solution is 12% or 13%. On the other hand, where color is of major importance, only enough brine may be added to bring the salt concentration of the, wash water or free solution up to, for instance, 8%. The practical limits of the percentage of salt concentration in the free solution may be greater than that stated. It may be as low as 5% and as high as 15% without seriously hampering the process. In general it may be stated that the higher the percentage of salt concentration the greater the yield of soap, and the lower the percentage the better the color, and

the percentage may be varied to best suit the requirements in any particular case. When the soap is properly grained out, the steam and agitator are shut off, the wash water separates out and is drawn off. Subsequent washes may be made without agitation by steam and at temperatures around F., which favor speedy separation. Usually about five washes will remove the greater part of oxidized and charred material contained in the soap stock. The color may be considerably lightened by the brine treatment and the alcohol elimination treatment should follow immediately after the final wash as some soaps tend to return in color.

In order to carry out the elimination of objectionable alcohols and proceed to the recovery of the relatively pure fatty acids and rosin acids, the washed soap is boiled up with water to form an emulsion. As the temperature of the emulsion passes F., further heating is brought about by introducing steam into the emulsion through the pipe coil in the bottom of the vessel and agitation is begun. At the same time, hydrochloric acid is introduced into the steam permeated and agitated emulsion as the temperature is raised from approximately 190 F. to boiling. Care should be taken in introducing the hydrochloric acid to be added should be determined beforehand by making a sample boil of the washed soap mechanical agitation is continued at boiling temperature until the emulsion has broken and for at least one hour thereafter, at which time the water layer should again betested for. acidity. If not acid, more acid must be added and heating and agitation continued for a few more minutes. When the water layer is still slightly acid. after the continued agitation the steam and agitator are shut off and the water layer drawn off. The saponifiable acids may then betransferred to a still or evaporator and dehydrated, and are then ready for further processing such as esterification, hydrogenation, etc.

If lighter colored saponifiable acids are desired, these acids recovered maybe bleached with clay, fullers earth, by any of the usual methods, or the soap may be bleached before the acid treatment by any of the methods common to the soap industry.

When the initial stock-to be treated is crude saponifiable acids, it should be saponified before carrying out the alcohol elimination treatment above described. This saponification may be 1. The method of removing higher alcohols and other impurities from crude soap stock and recovering the saponifiable acid content thereof in purified form, which comprises, forming an aqueous, emulsionof said-soap stock, heating said emulsion" and adding hydrochloric acid thereto in an amount suflicient to liberate the saponifiable acids and render the resulting mixture just acid to litmus after said emulsion has been broken, boiling said mixture while passing steam therethrough to break said emulsion and vaporize vaporizable compounds of said impurities and said hydrochloric acid from said mixture, continuing said boiling for a substantial period of time after breaking said emulsion while maintaining the mixture acid to litmus,

conducted in the same equipment, To carry-it out, the reaction vessel is charged with crude fatty acids and the temperature raised to 210 F,

by means of the steam coil and water jacket.

Caustic soda solution is then added in an amount predetermined by laboratory tests of the crude material. When saponification is complete, the soap thus formed is ready for processing'as de scribed above.

The acid used in the process must besuch that it will not only be liberated as steam or vapor at the temperature of the process, but it must not form compounds that will be insoluble in water or require a temperature higher than-boiling for liberation in the steamer vapor. acids form compounds with other materials such as the alcohols contained in the soap stock, and in order to be suitable for use in thevprocess described they should be such that the compounds they form will be capable of passing off as steam or vapor at about the boiling temperature.

Water is the cheapest dispersing agent, and the best acid is hydrochloric. Acetic acid would be of equal chemical advantage, but is more costly; sulphuric acid would be about the same in cost but could not be used'at steam tempera-.- ture. Hydrochloric acid is soluble in water and therefore thoroughly permeates the emulsion. It is highly reactive at the. temperature of steam, it will neutralize the alkali in the soap stock and is free to combine with the alcohols contained and to form compounds therewith that can be liberated at steam temperature. Consequently, when the acid has completed its reaction. and formed soluble compounds with the. alcohols, it and the compounds it has formed remain in:the water phase of the emulsionor pass oi as, steam or vapor.

The term saponifiable acids'. as used in the claims is employed in accordance with its use in the soap art to mean acids capableof reacting with alkalies to formvsoap.

What is claimed-is: I

Most

discontinuing said boiling and separating the liberated saponifiable acids from the aqueous portion'ofthe resulting mixture to remove water soluble compounds from said saponifiable acids.

2. The method'of removing-higher alcohols and other impurities from crude soap stock and recovering the saponifiable acid content thereof in purified form, which comprises, forming an aqueous emulsion of said soap stock, heating said emulsion and adding acetic acid thereto in an amount sufficient to liberate the saponifiable acids and render the resulting mixture just acid to litmus after said emulsion has been broken, boiling said mixture while passing steam therethrough to break said emulsion and vaporize vaporizable compounds of said impurities and said acetic acid 'from said mixture, continuing said boiling for a substantial period of time after breaking said emulsion while maintaining the mixture acid to litmus, discontinuing said boiling and separating the liberated saponifiable acids from the aqueous portion of the resulting mixture to remove water soluble compounds from said saponifiable acids.

3. The method of removing higher alcohols and other impurities from crude soap stock and recovering the saponifiable acid content thereof in purified form, which'comprises, forming an aqueous emulsion of said soap stock, heating said emulsion to a temperature of approximately F. and adding thereto sufiicient hydrochloric acid to liberate said saponifiable acids and render the resulting mixture just acid to litmus after said emulsion has been broken, boiling. said mixture while passing steam therethrough to break said emulsion and vaporize vaporizable compounds of said impurities and said hydrochloric acid from said mixture, continuing said boilingfor a substantial periodof time after breaking said emulsion while maintaining the mixture acid to litmus, discontinuing said boiling and separating the resulting saponifiable acids from the aqueous portion of the resulting mixture to remove water soluble compounds from said saponifiable acids.

4. The method of removing higher alcohols and other impurities from crude tall oil soap stock and recovering the saponifiable acid content thereof-in purified form, which comprises, forming an aqueous emulsion of said soap stock, heating saidgemulsion to a temperature of approximately 190 F. and adding thereto sufficient hydrochloric acid to liberate said saponifiable acids and render the resulting mixture just acid to litmus after said emulsion has been broken, boiling said mixture While passing steam therethrough to break said emulsion and vaporize vaporizable compoundsoi' said impurities and said hydrochloric acid from said mixture, continuing said boiling for at least an hour after said emulsion has been broken while adding a sufficient amount of hydrochloric acid to maintain the mixture acid to litmus, discontinuing said boiling and settling the resulting mixture to cause the resulting saponifiable acids to separate from the aqueous portion of said resulting mixture so as to remove water soluble compounds from said saponifi-able acids, and vaporizing re.- sidual water from said saponifiable acids,

5. The method of removing higher alcohols and other impurities from crude soap stock and recovering the saponiflable acid content thereof in purified form, which comprises forming an aqueous emulsion of said soap stock, heating said emulsion and adding a water soluble acid selected from the group consisting of hydrochloric acid and acetic acid to said emulsion in an amount sufilcient to liberate the saponifiable acids and render the resulting mixture just acid to litmus after said emulsion has been broken, boiling said mixture While passing steam therethrough to break said emulsion and to vaporize vaporizable compounds of said impurities and said water soluble acid from said mixture, continuing said boiling for a substantial period of time after breaking said emulsion while maintaining the mixture acid to litmus, discontinuing said boiling and separating the liberated saponifiable acids from the aqueous portion of the resulting mixture to remove water soluble compounds from said saponifiable acids,

6. The method of removing higher alcohols and other impurities from crude soap stock and recovering the saponifiable acid content thereof in purified form, which comprises, washing said crude soap stock with a brine solution to remove a portion of said impurities, forming an aqueous emulsion of said washed soap stock, heating said emulsion and adding thereto a water soluble acid selected from the group consisting of hydrochloric acid and acetic acid, said water soluble acid being added in sufficient amount to liberate the saponifiable acids and render said mixture just acid to litmus after said emulsion has been broken, boiling said mixture while passing steam therethrough to break said emulsion and to vaporize and remove said vaporizable compounds, continuing said boiling for a substantial period of time after breaking said emulsion while maintaining the mixture acid to litmus, discontinuing said boiling and separating the liberated saponifiable acids from the aqueous portion of the resulting mixture to remove said Water soluble compounds from said saponifiable acids.

BONHEUR M. WESTON. FRANK F. BEALL. 

